The standard for optical transport of telecommunications in North America is Synchronous Optical Network or SONET and its European variant is Synchronous Digital Hierarchy or SDH. The SONET and SDH standards specify a pre-defined hierarchy of synchronous payloads. However, the data rates needed by some services, such as asynchronous transfer mode (ATM) and Packet-over-SONET, exceed the capacity of the specified payloads. To accommodate high-speed data applications industry devised contiguous concatenation, which joins containers together to form a single structure that provides a higher data rate. Contiguous concatenation has some deficiencies, however, including an inability to efficiently accommodate finer granularity of payloads for some services. For example, a Gigabit Ethernet service (1000 Mbps) is traditionally transported over a SONET network using the nearest contiguous concatenation group size (i.e., OC-48c, which supports 2400 Mbps). Accordingly, nearly 60% of the bandwidth is wasted.
Virtual concatenation (VCAT) provides a mechanism for reducing bandwidth waste by producing appropriately sized pipes over the SONET network. VCAT divides the bandwidth into individual payload containers (e.g., STS-1 units). The individual containers are logically represented as members of the same virtual concatenation group or VCG. Members of a VCG are transported individually across the network to the destination, typically by way of different routes. The destination recombines the VCG members into a continuous bandwidth.
Bandwidth demands can fluctuate over the course of a day. For example, the need for increased bandwidth can arise in the evenings, during the early morning hours, and on weekends when enterprises often perform data backups over the network. To handle these demand fluctuations, a customer would prefer to purchase bandwidth sufficient to cover its daytime activity that increases to cover the demands of the evening. VCAT alone, however, cannot provide dynamic bandwidth allocation.
To achieve dynamic bandwidth allocation, industry devised Link Capacity Adjustment Schemes or LCAS to be used with VCAT. With LCAS, bandwidth allocated to service traffic over an optical link can be changed at any time without disrupting the traffic on the link. Using a two-way handshaking signaling protocol, LCAS can incrementally add and remove bandwidth capability within a VCG, without affecting the service or disabling the entire VCG. Service providers are thus able to supply bandwidth more closely in accordance with the customers' dynamically changing bandwidth needs. However, the combination of VCAT and LCAS technologies by itself does not enable service providers to prioritize and allocate bandwidth between services contending for use of a common link. There remains, therefore, a need for a system and method that can adaptively manage bandwidth on optical links shared by multiple services.